Resonant tunneling through a C60 molecular junction in liquid environment

We present electronic transport measurements through thiolated C$_{60}$ molecules in liquid environment. The molecules were placed within a mechanically controllable break junction using a single anchoring group per molecule. When varying the electrode separation of the C$_{60}$-modified junctions, we observed a peak in the conductance traces. The shape of the curves is strongly influenced by the environment of the junction as shown by measurements in two distinct solvents. In the framework of a simple resonant tunneling model, we can extract the electronic tunneling rates governing the transport properties of the junctions.Comment: 13 pages, 4 figures. To appear in Nanotechnolog

Mechanically controllable break junction in liquid environment : a tool to measure electronic transport through single molecules

This thesis discusses electronic transport measurements of single molecules in a liquid environment with the ultimate goal of demonstrating a molecular transistor addressed by a liquid gate. A mechanical controllable break junction with an integrated liquid cell is used as the measurement tool. We first studied the influence of different solvents on the conductance of gold junctions in the regime of tunneling and true metallic contacts. These measurements served as control experiment for the electrical characterization of single molecules. We then measured the conductance traces of thiolated C60 molecules while varying the electrode separation. The shape of the curves was found to be strongly influenced by the solvent. By using a resonant tunneling model, the electronic tunneling rates could be extracted. Finally, the effect of a liquid gate was tested on several tetrathiafulvalene (TTF) compounds. This thesis is organized in the following way. • The first chapter presents two different approaches for producing nanogaps in order to contact single molecules. One is based on electrochemical wires grown in pores, whereas the other method concerns the electrochemical narrowing of lithographically defined gaps. • The second chapter introduces the break junction and gives a short overview over its research field. Discussed are the geometry and the mechanical properties of the break junction and finally the conductance of atomic contacts. • Chapter 3 is dedicated to the fabrication of break junction samples and the measurement setup. • Electric conductance measurements of atomic contacts in liquid environments are presented in the forth chapter. This work was done with the perspective of measuring single molecules in the break junction. Also discussed is tunneling through alkanethiols. • Chapter 5 presents electric transport measurements through thiolated C60 molecules in a liquid environment. When varying the electrode separation a peak in the conductance traces has been observed. By applying a resonant tunneling model, we were able to extract electronic tunneling rates. • In Chapter six transport measurements through tetrathiafulvalene (TTF)-based molecules with an electrochemical gate are shown. A possible gate effect is discussed based on the I-V characteristics

Stoma-free Survival After Rectal Cancer Resection With Anastomotic Leakage: Development and Validation of a Prediction Model in a Large International Cohort.

Objective:To develop and validate a prediction model (STOMA score) for 1-year stoma-free survival in patients with rectal cancer (RC) with anastomotic leakage (AL).Background:AL after RC resection often results in a permanent stoma.Methods:This international retrospective cohort study (TENTACLE-Rectum) encompassed 216 participating centres and included patients who developed AL after RC surgery between 2014 and 2018. Clinically relevant predictors for 1-year stoma-free survival were included in uni and multivariable logistic regression models. The STOMA score was developed and internally validated in a cohort of patients operated between 2014 and 2017, with subsequent temporal validation in a 2018 cohort. The discriminative power and calibration of the models' performance were evaluated.Results:This study included 2499 patients with AL, 1954 in the development cohort and 545 in the validation cohort. Baseline characteristics were comparable. One-year stoma-free survival was 45.0% in the development cohort and 43.7% in the validation cohort. The following predictors were included in the STOMA score: sex, age, American Society of Anestesiologist classification, body mass index, clinical M-disease, neoadjuvant therapy, abdominal and transanal approach, primary defunctioning stoma, multivisceral resection, clinical setting in which AL was diagnosed, postoperative day of AL diagnosis, abdominal contamination, anastomotic defect circumference, bowel wall ischemia, anastomotic fistula, retraction, and reactivation leakage. The STOMA score showed good discrimination and calibration (c-index: 0.71, 95% CI: 0.66-0.76).Conclusions:The STOMA score consists of 18 clinically relevant factors and estimates the individual risk for 1-year stoma-free survival in patients with AL after RC surgery, which may improve patient counseling and give guidance when analyzing the efficacy of different treatment strategies in future studies